Submission #836762

#	Time	Username	Problem	Language	Result	Execution time	Memory
836762		becaido	Thousands Islands (IOI22_islands)	C++17	100 / 100	262 ms	50092 KiB

islands

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx,popcnt,sse4,abm")
#include <bits/stdc++.h>
using namespace std;

#ifndef WAIMAI
#include "islands.h"
#endif

#ifdef WAIMAI
#define debug(HEHE...) cout << "[" << #HEHE << "] : ", dout(HEHE)
void dout() { cout << "\n"; }
template<typename T, typename...U>
void dout(T t, U...u) { cout << t << (sizeof...(u) ? ", " : ""), dout(u...); }
#else
#define debug(...) 7122
#endif

#define ll long long
#define Waimai ios::sync_with_stdio(false), cin.tie(0)
#define FOR(x,a,b) for(int x = a, I = b; x <= I; x++)
#define pb emplace_back
#define F first
#define S second

const int SIZE = 1e5 + 5;

int n, m, s;
bool state[2 * SIZE];
vector<int> ans, chain;
set<pair<int, int>> adj[SIZE], rev[SIZE];

queue<int> q;
void deal() {
    while (q.size()) {
        int pos = q.front();
        q.pop();
        for (auto [np, id] : rev[pos]) if (adj[np].size()) {
            adj[np].erase({pos, id});
            if (adj[np].size() == 0) q.push(np);
        }
    }
}

int cnt;
void dfs(int pos, int last) {
    if (pos == s && last != -1 && cnt == 0) return;
    for (auto [np, id] : adj[pos]) if (id != last) {
        cnt -= state[id];
        adj[pos].erase({np, id});
        adj[np].emplace(pos, id);
        state[id] ^= 1;
        ans.pb(id);
        cnt += state[id];
        dfs(np, id);
        return;
    }
}

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
    n = N, m = M;
    FOR (i, 0, m - 1) {
        adj[U[i]].emplace(V[i], i);
        rev[V[i]].emplace(U[i], i);
    }

    FOR (i, 0, n - 1) if (adj[i].size() == 0) q.push(i);
    deal();

    while (adj[s].size() <= 1) {
        q.push(s), deal();
        if (adj[s].size() == 0) return false;
        auto [np, id] = *adj[s].begin();
        chain.pb(id);
        s = np;
    }

    FOR (i, 0, n - 1) while (adj[i].size() > 1 + (i == s)) adj[i].erase(adj[i].begin());
    dfs(s, -1);

    ans.insert(ans.begin(), chain.begin(), chain.end());
    reverse(chain.begin(), chain.end());
    ans.insert(ans.end(), chain.begin(), chain.end());
    return ans;
}

/*
in1
4 5
0 1
1 2
2 3
0 3
3 1
out1
1
10
0 1 2 4 0 3 2 1 4 3

in2
2 3
0 1
1 0
1 0
out2
0
0
*/

#ifdef WAIMAI
int main() {
  int N, M;
  assert(2 == scanf("%d %d", &N, &M));

  vector<int> U(M), V(M);
  for (int i = 0; i < M; ++i) {
    assert(2 == scanf("%d %d", &U[i], &V[i]));
  }

  variant<bool, vector<int>> result = find_journey(N, M, U, V);
  if (result.index() == 0) {
    printf("0\n");
    if (get<bool>(result)) {
      printf("1\n");
    } else {
      printf("0\n");
    }
  } else {
    printf("1\n");
    vector<int> &canoes = get<vector<int>>(result);
    printf("%d\n", static_cast<int>(canoes.size()));
    for (int i = 0; i < static_cast<int>(canoes.size()); ++i) {
      if (i > 0) {
        printf(" ");
      }
      printf("%d", canoes[i]);
    }
    printf("\n");
  }
  return 0;
}
#endif

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 21 / 21
• Subtask 4: 24 / 24
• Subtask 5: 45 / 45